1. Field of the Invention
The present invention relates to a reforming apparatus and its method of driving and a fuel cell system including the reforming apparatus. More particularly, the present invention relates to an oxidation reactor that generates thermal energy from an oxidation reaction of a fuel using a catalyst.
2. Description of the Related Art
As is well known, a fuel cell is an electricity generating system for generating electrical energy using a fuel and an oxidant gas. The fuel cell may be either a polymer electrolyte membrane fuel cell or a direct oxidation membrane fuel cell.
The polymer electrolyte membrane fuel cell receives a reformate gas generated in a reforming apparatus and an oxidant gas that is different from the reformate gas, and generates electrical energy in an oxidation reaction of hydrogen contained in the reformate gas and an electrochemical reaction of oxygen contained in the oxidant gas.
The reforming apparatus has a heater that generates thermal energy by combustion of a fuel, and a reforming reactor that generates a reformate gas in a reforming reaction of the fuel using the thermal energy.
The heater can be either a burner-type heater or an oxidation-type heater. The burner-type heater generates thermal energy by direct combustion of a fuel containing a liquid fuel, such as methanol and ethanol, and a gas fuel, such as LPG and LNG, and the oxidation-type heater generates thermal energy from an oxidation reaction of the fuel.
The burner-type heater has drawbacks of difficulty in driving and reducing a life-cycle of the entire reforming apparatus because a flame causes a hot-spot phenomenon of the burner. Thus, a sufficient space for the burner is required for eliminating the hot-spot phenomenon, and accordingly, the volume of the entire apparatus is increased.
The oxidation-type heater includes an oxidation reactor that generates thermal energy by using an oxidation method of the fuel. However, particularly when using the gas fuel, the oxidation reactor cannot generate the oxidation reaction of the gas fuel by the oxidation catalyst at room temperature, and therefore the oxidation catalyst needs to be preheated to a predetermined temperature.
Conventionally, a preheating apparatus for directly or indirectly heating the oxidation catalyst using an electric heater, such as a heat wire, or directly heating the oxidation catalyst using a flame, such as a burner, has been disclosed in order to solve the above problems.
However, the conventional oxidation reactor using the electric heater requires an increased number of parts, and consumes power from a fuel cell.
In addition, the conventional oxidation reactor using the burner is difficult to drive so that the oxidation catalyst is sintered or damaged due to the flame.